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Comparison · Pregnancy Smart

Bottled vs filtered vs tap water in pregnancy

Assigned clinical reviewerPerry Friedman· MD, FACOG-MFMDraft · pending clinical reviewUpdated

How do the options compare?

The comparison below weighs mainstream OB guideline standing, the depth of the pregnancy evidence base, dosing clarity, expected onset, and interactions worth flagging to your provider.

OptionStudied pregnancy doseGuideline supportNotes
Tap water (public supply)Regulated; median nitrate around 5.0 mg/L in US public supplies, per one national studyMeets regulatory standards, but research has found rising small-for-gestational-age risk even below those standards, and PFAS was detected in most unfiltered samples in one paired studyLeast expensive and lowest plastic waste; quality varies by local utility, so checking your area's water quality report is worthwhile
Filtered tap waterVaries by filter type: activated carbon vs. reverse osmosisReverse osmosis removed PFAS entirely in one study; standard carbon filters reduced some PFAS by about half but did not eliminate it, and are not generally effective against nitrateFilter type matters more than the fact of filtering; check independent certification for the specific contaminant you're targeting
Bottled waterMedian nitrate around 0.33 mg/L in one US study, well below tap or well waterLowest measured nitrate of the three sources, but not shown to be lower in PFAS than tap water in paired testingAdds cost and plastic waste, and water stored in plastic is a contributor to microplastic exposure, which has been detected in human placental tissue
  • In one study, PFAS were detected in the majority of unfiltered tap water samples tested, activated-carbon filtering reduced detection rates for some PFAS compounds by roughly half, and reverse-osmosis filtered water had no detectable PFAS at all. 1
  • In that same study, PFAS levels measured in the blood of pregnant participants did not differ significantly between those who drank unfiltered tap water and those who drank bottled water, suggesting bottled water isn't automatically lower in PFAS exposure. 1
  • A nationwide study of over one million births found that small-for-gestational-age risk rose with tap water nitrate exposure even at levels below current regulatory limits, with a 2 percent increase in risk for every tenfold increase in nitrate concentration. 2
  • Median nitrate levels varied sharply by water source in a US birth defects study: about 0.33 mg/L in bottled water, 5.0 mg/L in public tap water supplies, and 17.6 mg/L in private wells, and daily nitrate intake of 5 mg or more from drinking water was linked to roughly double the risk of spina bifida. 3
  • Microplastics, including polyethylene from plastic packaging, have been detected in drinking water at concentrations up to 10,000 particles per liter and have also been found in human placental tissue, an exposure route that applies to water stored in plastic bottles as well as, to a lesser extent, tap water carried through plastic-containing infrastructure. 4

Which option makes sense?

The options above differ in their evidence, limitations, and suitability. Inclusion in this comparison is not a recommendation. Please consult your healthcare provider before making a decision based on these findings.

Disclosure: Pregnancy Smart is a supplement maker. The options compared above sit outside our own product line; this page describes their pregnancy evidence on its own merits.

Frequently asked questions

Is bottled water safer than tap water during pregnancy?

Not automatically. Bottled water tends to be lowest in nitrate, but research hasn't found it to be meaningfully lower in PFAS than tap water, and it comes with its own plastic-related microplastic exposure. The safer choice depends on what's actually in your specific tap water.

Do pitcher filters remove lead?

Many carbon pitcher filters are certified to reduce lead, but certification and performance vary by brand and filter age. Check your specific filter's certification (commonly against NSF/ANSI standards) rather than assuming any filter removes it.

Does filtering remove nitrates or PFAS?

It depends on the filter type. Standard activated-carbon filters reduced some PFAS compounds by roughly half in one study but did not eliminate them, while reverse-osmosis filtering removed PFAS entirely. Standard carbon filters are not generally effective at removing nitrate; reverse osmosis is the more reliable option for both contaminants.

Is mineral water fine during pregnancy?

Yes, mineral water is a reasonable choice, though the same nitrate and microplastic considerations that apply to other bottled water apply here too. Check the label or the bottler's water quality report if you have concerns.

Which filter certification should you look for?

Look for a filter independently certified to reduce the specific contaminant you're concerned about (lead, PFAS, or nitrate are tested separately), rather than assuming a general-purpose filter covers all three.

Related in the library

References

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.